GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 DTC 🢒 DTC P1546

Circuit Description

The powertrain control module (PCM) will activate the A/C clutch relay when the PCM detects that A/C has been requested. When the PCM activates the relay, voltage should be present at both the A/C compressor clutch and the A/C compressor clutch supply voltage circuits at the PCM. If voltage is not detected when A/C is requested this C type DTC sets.

Conditions for Running the DTC

The ignition is turned ON.

The A/C clutch is requested.

Conditions for Setting the DTC

The PCM commands the A/C ON and the PCM does not detect a voltage on the A/C clutch status line for more than 5 seconds.

Action Taken When the DTC Sets
    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM records the operating conditions at the time the diagnostic fails.
    • The PCM stores this information in the Failure Records.
    • The multifunction display (MFD) in the instrument cluster will display a message at key-on and key-off.

Conditions for Clearing the DTC
    • The DTC will become history if the PCM no longer detects a failure.
    • The history DTC will clear after 40 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Verifies that battery voltage is supplied to the A/C compressor clutch relay.

    2.

  2. Tests if the A/C relay is at fault or the A/C compressor clutch supply voltage circuit is at fault. If the A/C compressor clutch engages, this indicates that the A/C compressor clutch supply voltage circuit is OK.

    3.

  3. If the A/C clutch feedback signal parameter displays OFF, this indicates that the A/C compressor clutch supply voltage circuit is open between the splice and the PCM. If the A/C clutch feedback signal parameter displays ON, this indicates a faulty connection at the A/C compressor relay or a malfunctioning relay.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

Important: Diagnose P0645 first if it is set.

  1. Install a scan tool.
  2. Start the engine.
  3. Turn ON the A/C and let the engine idle for 5 minutes.
  4. Observe the A/C Clutch Feedback Signal parameter.

Does the A/C Clutch Feedback Signal parameter display ON when the A/C clutch is engaged?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the A/C compressor clutch relay ignition 1 voltage circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 4

4

Install a 15-amp fused jumper wire between the A/C compressor clutch relay ignition 1 voltage circuit and the A/C compressor clutch supply voltage circuit.

Does the A/C compressor clutch engage?

Go to Step 5

Go to Step 9

5

Important: The fused jumper wire should still be installed with the ignition on.

With a scan tool, observe the A/C Clutch Feedback Signal parameter.

Does the scan tool indicate that the A/C Clutch Feedback Signal parameter is ON?

Go to Step 7

Go to Step 6

6

Test the A/C compressor clutch supply voltage circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

8

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

Repair the A/C compressor clutch supply voltage circuit between the A/C compressor clutch relay and the A/C compressor clutch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 12

--

10

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement .

Did you complete the replacement?

Go to Step 12

--

11

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the replacement?

Go to Step 12

--

12

  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK